California laws restricting the type and quality of food and drinks for sale in public schools appear to have improved childhood obesity and overweight trends, but progress was better among children at schools in more affluent communities, according to a study published Monday in the journal JAMA Pediatrics.

In the five years after the start of these statewide policy changes, trends in overweight/obesity leveled off among fifth-grade students at public schools in socioeconomically disadvantaged neighborhoods and declined in advantaged neighborhoods, according to the study led by researchers at San Francisco State University.

The researchers looked at the effect of two state laws enacted over the past decade that restricted so-called “competitive food and beverages” (CF&Bs), which are sold alongside meal programs in public schools.

SB 677 — effective July 1, 2004 — prohibited the sale of sugary beverages in elementary and middle schools (kindergarten through eighth grade), and required drinks for sale on campus to contain at least 50% fruit juice with no added sweeteners. The law also limited fat content of milk to 2%. SB 12 — effective July 1, 2007 — set portion and nutrition size standards for CF&Bs sold in elementary and middle schools. Snacks sold in elementary schools, for instance, must limit the percentage of total calories from saturated fats to 10% and sugar content to 35%. SB 12 also expanded beverage standards of SB 677 to public high schools.

The study included more than 2.7 million fifth-graders in 5,362 California public schools from 2001 to 2010. The researchers compared overweight/obesity prevalence trends before (2001 to 2005) and after (2005 to 2010) the two laws took effect. Data sources included the Fitnessgram database available from the California Department of Education, school and district data and 2000 U.S. Census data.

Before the policy changes, the prevalence of overweight/obese fifth-graders ticked higher each year from 2001 to 2005, climbing from 43.5% to 45.3% in that period. However, that overweight/obese prevalence stabilized over the following five years. Overweight/obese prevalence in fifth-graders was 46.2% in 2006 and 45.8% in 2010, according to the study.

The least advantaged neighborhoods were likely to have the highest prevalence of children considered overweight or obese, the study authors found. In 2010, prevalence was 52.8% for fifth-graders in the lowest-income neighborhood, compared to 36.2% for fifth-graders in the highest-income neighborhood.

“These findings suggest that CF&B policies may be crucial interventions to prevent child obesity,” said Emma Sanchez-Vaznaugh, assistant professor in health education at San Francisco State University and lead study author. “But the degree of their effectiveness is also likely to depend on influences of socioeconomic resources and other contextual factors within school neighborhoods,” she added.